Localized myofascial pain responds better than referring myofascial pain to botulinum toxin injections.

Myofascial pain of the muscles of mastication is a common temporomandibular disorder. Patients unresponsive to conservative treatment modalities pose a therapeutic challenge to the treating clinician. The efficacy of intramuscular botulinum toxin injections for recalcitrant cases is still not well established due to mixed results from clinical trials. The Diagnostic Criteria of Temporomandibular Disorders (DC/TMD) classified chronic muscle pain broadly into a localized pattern (when pain is localized to the site of palpation or the muscle palpated) and a referring pattern (when the pain spreads beyond the boundary of the muscle being palpated). The medical records of 25 consecutive patients treated with botulinum were analysed retrospectively. Significant pain reduction was achieved in 69.2% of the patients with localized myofascial pain and 16.7% of the patients with referring myofascial pain (P=0.015). Seventy-seven per cent of the patients with localized myofascial pain reported using less analgesic throughout the follow-up period, whereas only 25% of the patients with referring myofascial pain (P=0.017). The effects of botulinum toxin in responsive patients subsided after a mean of 3.21 months. Patients with localized myofascial pain benefited from botulinum toxin injections, but patients with referring myofascial pain responded poorly to this treatment.